Classification of plant diseases

Whole types of classification methods are discussed and explained briefly.

1. Muhammad Saeed Siddiqui Department of Botany GPGC No 1 Abbottabad Roll No: BOT-19-27

2. By Muhammad Saeed Siddiqui Classification of Plant Diseases

3. Classification on the basis of different criteria : M ode of perpetuation and primary infection. Infectious nature. Production and spread of the inoculums or number of pathogen generations. Extents of plant parts affected. Causes of the disease. Occurrence and geographic distribution. Plant part affected. Crop plants affected. Symptoms produced on host plants.

4. On the basis of Mode of perpetuation and primary infection: It is of three types Soil borne diseases Air borne diseases Seed borne diseases

5. Soil borne diseases The pathogen survive in the soil or on the infected plant debris lying in the soil either as their resting spore or as mycelia strand. They all attack the root system of host plants. E.g Damping off ( Pythium sp. ), seedling blight ( phytophthora , Fusarium sp. )

6. Air borne diseases Some pathogen infect the host plant through air and bring primary and secondary infection. E.g. Rusts, powdery mildews Seed borne diseases Some pathogen survive as dormant mycelium or other propagative structures in the seeds of host plants. E.g. Loose smut of wheat (internally seed borne)

7. On the basis of infectious nature 1) infectious plant diseases: These disease are caused by living agents, the pathogen. All the pathogens are parasitic on plants . These are characterized by the ability of the pathogen to grow and multiply rapidly. e.g. Powdery mildew, Rusts 2) Non-infectious diseases: These disease do not spread from plant to plant (non infectious). These are caused by abiotic factors ( Physiological disorder, lack of nutrients). e.g. black heart of potato (lack of oxygen)

8. On the basis of production and spread of the inoculum or number of pathogen generation Single cycle or monocyclic disease: The increase of disease is mathematically analogous to simple interest money. Those disease which have only generation in one cropping season. E.g. loose smut of wheat

9. On the basis of production and spread of the inoculum or number of pathogen generation Multiple cyclic or polycyclic disease: The increase in disease is mathematically analogous to compound interest of money. Those disease which have more than one generation in a cropping season. E.g. late blight of potato

10. On the basis of production and spread of the inoculum or number of pathogen generation Polyetic diseases: These are also polycyclic diseases but they complete their disease cycle in more than one year. e.g. Cedar apple rust

11. On the basis of extent of plant parts affected Localized: If they affect only specific organ or parts of the plants. e.g. Root rot, leaf spot 2. Systematic: If entire plant is affected. e.g. downy mildew, Damping off

12. On the basis of cause of the disease Three types of diseases on the basis of the cause Biotic disease Fungal disease, bacterial disease, phytoplasma disease, phanerogamic disease, nematode disease. 2. Mesobiotic disease Disease caused by virus or viroid . 3. Abiotic disease By abnormal environmental condition

13. On the basis of occurrence and geographic distriution Epidemic disease: A disease usually occurs widely but periodically in a destructive form is reffered as epidemic or epiphytotic disease. e.g. late blight of potato – Irish famine (1845)

14. On the basis of occurrence and geographic distriution 2. Endemic: Constantly present in a moderate to severe from and is confined to a particular country or ditrict . e.g. club root of cabbage in Nilgiris , black wart of potato and onion smut

15. On the basis of occurrence and geographic distriution Sporodic disease Occur at very irregular intervals and locations and in relativity fewer instances. e.g. udbatta disease of rice, angular leaf spot of cocumber

16. On the basis of occurrence and geographic distriution Pandemic disease An epidemic occuring worldwide, or over a very wide area, crossing international boundaries and usually affecing a large number of population. e.g. Wheat rust UG99

17. On the basis of organ and plant part affected Fruit disease e.g Apple scab Root disease e.g. Root rot of papaya Leaf disease e.g. Leaf spot of cotton Seedling disease e.g. damping off of seedling

18. On the basis of crop plant affected Cereal disease e.g. wheat, barley and oat Pulses disease e.g. ascochyta blight of chickpea Millet disease e.g. green ear disease of bajra Vegetable disease e.g. early blight of tomato Fruit disease e.g. apple scab Ornamenatal plant disease e.g. chrysanthimum stunt Forests plant diseases e.g. sudden oak death

19. On the basis of symptoms produced on host plants Downy mildew Symptoms appears as yellow to white patches on the uper surface of leaves. This disease is caused by family peronosporaceae (Fungus). e.g. DMD of grapevine

20. On the basis of symptoms produced on host plants 2. Powdery mildew Symptoms appears as white powdery mass on upper surface of leaves, inflorescence. E.g. mango powdery mildew, Pea PMD

21. On the basis of symptoms produced on host plants Leaf curls Curling, thickening and distoration of leaves. E.g. peach leaf curl (Fungus), Tomato leaf curl (Virus)

22. On the basis of symptoms produced on host plants Galls Enlarged parts of plant organs, usually caused by excessive multiplication or enlargement of plant cells. E.g. clubroot – enlarged root, bacterial gall by agarobacterium

23. On the basis of symptoms produced on host plants Scab A roughened, crust-like diseased area on the surface of a plant organ. E.g. apple scab and pear scab

24. On the basis of symptoms produced on host plants Dieback Progressive death of shoots and twigs generally starting at the tip of infected plant part. E.g. shoot dieback of apple

25. On the basis of symptoms produced on host plants Anthracnose Damping off Rots Leaf spot Blight Spot blotch Rusts Canker Smut Wilt

26. Thanks for your attention Submitted to Professor Sarfaraz sb of department of Government Postgraduate College No 1 Abbottabad